Methods and apparatuses for electrically controlled assistance to a vehicle movement are generally known and are widely used in modern motor vehicles. By way of example, one driving assistance system in a motor vehicle is an electronic stability management system, ESP. In this system, the brakes and engine in the motor vehicle can normally be operated in a suitable manner to keep the motor vehicle in a stable driving state or to bring it to a stable driving state from an unstable driving state.
The driving assistance system is supplied with motor vehicle states, determined by various sensors, and/or the driving motion of the motor vehicle, as input variables. Output variables are determined from these input variables in order to control actuators which can act on the driving movement of the motor vehicle, for safety purposes. Intended values to be achieved for the characteristic variables of the vehicle movement are normally predetermined for the driving assistance system. Compliance with these intended values ensures that the motor vehicle is driving in a stable state. In this case, it is important for these intended values to be predetermined correctly and exactly in order that the driving assistance system can set the stable driving behavior of the motor vehicle safely, quickly and reliably.
By way of example, one undesirable driving movement is oversteering of the motor vehicle. Oversteering of a vehicle is defined as the situation when the slip angle of the rear wheels of the vehicle is greater than the slip angle of the front wheels. This means that the rear of the vehicle breaks away, that is to say it slides outwards in a curve. The expression “oversteering” is also used to characterize the natural steering behavior of vehicles. The opposite behavior is referred to as understeer. The natural tendency of a vehicle to try to “turn more” than has been selected on the steering wheel is in principle regarded as being less safe than understeering.
When a vehicle starts to oversteer or understeer, the vehicle can, for example, be stabilized by means of an appropriate steering action by the driver, for example by the driver steering in the opposite direction. Opposite steering requires a certain amount of practice. Inappropriate opposite steering by inexperienced drivers can, in some cases, cause accidents with considerable personal injuries. There is a need for a method and an apparatus which make it possible to achieve safe stabilization of the vehicle in the event of oversteer, or at the onset of oversteer.